If the Cupertino, Calif., company follows past practice, it will add El Capitan to the Mac App Store around 10 a.m. PT.

The upgrade will run on the same Macs that now run last year's Yosemite, 2013's Mavericks, 2012's Mountain Lion and 2011's Lion, according to Apple's system requirements. That means more than nine of out 10 Macs which were online in August should be able to install El Capitan.

This year's version of OS X will be the third that Apple has handed out for free, a zero-dollars pricing it introduced with Mavericks. That, in turn, should trigger an immediate surge in its user share, an estimate of the percentage of all Macs running the operating system. The last two editions, Yosemite and Mavericks, accumulated user shares of 37% and 32%, respectively, by the end of their first full month of availability.

Apple has billed El Capitan as a performance, stability and reliability upgrade from Yosemite, but it does offer several new or improved features and enhanced applications, including natural-language search and split-screen mode, and a slicker Mail client and beefed-up Notes app.

El Capitan will almost certainly take the front-and-center spot in the Mac App Store when it's released. To reach the e-mart, Mac owners must click on the icon in the Dock or select "App Store..." from the Apple menu at the left of the menu bar.

This story, "OS X El Capitan launches Wednesday" was originally published by
Computerworld.